1. Field of the Invention
The present invention relates to a web camera which sends a photographed moving image to a terminal such as a PC, a cellular phone and the like, after converting the moving image to a format suitable for the terminal type.
2. Background Arts
A web camera installed in, for example, tourist destinations or famous spots sends photographed moving image data to viewers' PCs (personal computers) through the Internet. Received moving image data is reproduced as the moving image on a monitor of the PC by use of a web browser. By using a streaming mode which concurrently receives and reproduces moving image data, viewers can see almost live moving images of the spots.
Recently, however, there is a need to see the moving image photographed by the web camera with a cellular phone or a communication-capable PDA (Personal Digital Assistant) which are widely used. The web browsers installed in the cellular phone and the PDA do not support the reproduction of the moving image in the streaming mode. Thus, the viewer cannot see moving image but static images of the photographed moving image.
An animation GIF (Graphics Interchange Format) is generally known as the moving image format which the cellular phone and the PDA can reproduce. The animation GIF (GIF animation) is widely used to reproduce, for example, a banner advertisement on a homepage of WWW (World Wide Web). A single animation GIF file is composed of a plurality of GIF images. Continuously displaying the plurality of GIF images makes it possible to reproduce a moving image.
Japanese Patent Laid-Open Publication No. 2000-092437 discloses a digital camera which outputs an animation GIF file. Upon pressing a shutter button, the digital camera makes continuous exposures at predetermined intervals. Continuously exposed image data is subject to a subtractive color process, and then is compressed with the LZW (Lempel Ziv Welch) method. Compressed data of a plurality of images is compiled into the single animation GIF file which is written into a flexible disk.
By use of a web camera which converts the photographed moving image into the animation GIF file, as described above, it is possible to reproduce the moving image with the cellular phone and the PDA. The maximum number of color of the animation GIF file, however, is 8 bits (256 colors), so that the animation GIF file lacks expressive power for the monitor of a PC which can display 24 bit (16.77 million) colors. Furthermore, since the frame rate (the number of picture frames per second) of the animation GIF is generally less than that of the streaming mode, the quality of the animation GIF file is unsatisfactory when the moving image is reproduced on the monitor of the PC.